Steering arrangement for a work machine

ABSTRACT

A steering arrangement is provided for a work machine that includes a braking device, actuated by an actuation switch, to hold an operator input device in a predetermined position during operation. The braking force of the braking device can be overcome by the operator to make steering adjustments. The work machine may include a second steering arrangement on an opposite side of the work machine to improve operator visibility during close operation. A selector switch is used to select between one or the other steering arrangements.

TECHNICAL FIELD

[0001] The present invention relates generally to a steeringarrangement, and more particularly to a steering device with a springreturn and position locking arrangement.

BACKGROUND

[0002] Steering arrangements not having a mechanical connection betweenthe steering wheel and the ground engaging support members are commonlyknown in work machines. These known arrangements accept steering inputcommands from the operator through the use of a lever, joystick,steering wheel, or other input device. The steering input commands aretransformed to an electric signal that is then transmitted to acontroller that sends an electronic signal, responsive to the magnitudeof the steering command, to a pump, valve, motor or other mechanicaldevice to turn wheels, speed or slow tracks to actually perform theturning operation.

[0003] One example of such a steering apparatus is disclosed in U.S.Pat. No. 4,771,846 issued on Sep. 20, 1988 to Fredrick Venable et al.and is assigned to TRW, Inc. This patent shows a steering system forcontrolling a vehicle with steerable wheels. The system includes asteering wheel having a steering sensor attached thereto. A signalrepresentative of a desired turning command is transferred from thesensor to a controller. The controller in turn delivers a signal to ahydraulic control valve that controls the flow of fluid to a hydraulicmotor that is in turn connected to the steerable wheels.

[0004] This steering system also provides the operator with a steeringfeedback/feel that is provided by an electromagnetic friction brake. Thecontroller in response to a steering wheel position sensor and a steeredwheel position sensor controls the electromagnetic brake. The amount offriction force created by the electromagnetic brake depends upon and islimited by the strength of the electromagnet. However this patent isdirected towards automobiles that travel at much higher speeds thatrequire constant operator intervention. The patent is also absent anyway of dealing with operator fatigue and multi-tasking that an operatorof a work machine faces during operation of such a machine.

[0005] The present invention is directed to overcoming one or more ofthe problems as set forth above.

SUMMARY OF THE INVENTION

[0006] In one aspect of the present invention a steering arrangement isprovided for a work machine. The work machine includes at least twoground engaging support members positioned on opposite sides of the workmachine. A steering motor is connected to each of the ground engagingsupport members. Each steering motor operatively propels and steers theground engaging support members in response to a control signal. Thesteering arrangement includes a support member and a steering inputdevice movable relative to the support member. A biasing mechanism ispositioned between the support member and the steering input device. Asensor is positioned to sense the position of said input device andproduces an electrical signal indicative of the position. Anelectromagnetic brake is connected to the input device and the support.A switch is connected to the electromagnetic brake.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a schematic representation of a work machine embodyingthe present invention;

[0008]FIG. 2 is a schematic illustration of a steering arrangementembodying the present invention; and

[0009]FIG. 3 is a sectional view of a portion of the steering systemshown in FIG. 2.

DETAILED DESCRIPTION

[0010] Referring now to the drawings and particularly to FIG. 1, a workmachine 10 such as an asphalt paver is shown having at least two groundengaging support members 12 one each positioned on opposite sidesthereof. The ground engaging support members 12 are shown as beingtracks, however wheels, rubber belts or other suitable support members12 would work equally as well.

[0011] A steering system 14 for the work machine 10 is shown andincludes a steering motor 16 connected with each of the ground engagingsupport members 12 for supplying power thereto. Steering motors 16 areshown as being fixed displacement fluid motors but alternatively may beelectric motors and still function in a similar manner. Each steeringmotor 16 is connected to a multi-speed planetary gear arrangement 18having a drive wheel 20 that directly operatively engages one of theground engaging support members 12. The multi-speed planetary geararrangements 18 allow for at least two speed ranges such as roading andpaving. Individual propel pumps 22 supply operative power to arespective steering motor 16. The propel pumps 22 are shown for exampleas being variable displacement pumps but could be other known devicesthat would supply a variable amount of power output, such as electricalgenerators, to propel work machine 10. In the example shown in FIG. 1the propel pumps 22 are connected to and draw fluid from and areconnected to a fluid reservoir 24 via conduits 26. An engine 28 isoperatively connected to the propel pumps 22 in a known manner.

[0012] A steering arrangement 30 is connected to an electric controlmodule 32. The steering arrangement 30 supplies a steering signalresponsive to the magnitude and direction of an operator steering inputrequest to the electric control module 32 as will be described below.Control module 32 is connected and sends electrical signals to each ofthe propel pumps 22. The control module 32 in turn, supplies a steeringoutput command signal to each of the propel pumps 22 that is responsiveto the magnitude and direction of the desired input request from theoperator.

[0013] Steering direction is thus controlled by actuation of the propelpumps 22. The steering rate and direction is proportional to the amountof fluid flow supplied to and from the steering motors 16, which arecontrolled by controlling the displacement of the respective propelpumps 22. The propel pumps 22 are responsive to the magnitude of thesignal from control module 32 being outputted to the pumps 22. Forexample, if a right hand turn is desired the propel pump 22 thatsupplies pressurized fluid to the right steering motor 16 reduces outputand the propel pump 22 that supplies pressurized fluid to the leftsteering motor 16 increases output respectively in response to themagnitude of the turn request. Thus speeding the rotation of the lefthand support member 12 and slowing the rotation of the right handsupport member 12 to maneuver the desired right hand turn.

[0014] The control module 32 receives operating power from a battery 34through an ignition switch 36 when the ignition switch 36 is placed in aclosed/run position. The work machine 10 may include an additionalsteering arrangement 30′. The additional steering arrangement 30′ isconnected to the control module 32 in the same manner as steeringarrangement 30 and allows the operator to sit on either side of the workmachine 10 during operation and still retain steering control of thework machine 10 while working close to curbs bridge railings and thelike. A selector switch 38 positioned on the operator control panel (notshown) is used to select between steering arrangement 30 or steeringarrangement 30′. In this example, the term selector switch 38 means anyof a number of known switching devices that may be used to selectbetween steering arrangement 30 and steering arrangement 30′. Steeringarrangement 30′ is substantially operatively and structurally similar tosteering arrangement 30 and therefore only steering arrangement 30 willbe described in detail.

[0015] Referring now to FIGS. 2 and 3 steering arrangement 30 includesan operator input device 40, which is for example a steering wheel, thatis connected to one end of an input shaft 42. Input shaft 42 ispositioned within a support tube 43 and rotatably supported at both endsby means of a pair of bearings/bushings 44 (only one shown in FIG. 3).Support tube 43 is connected to a stationary support 46 by a mountingplate 45 that holds one of the bearing/bushings 44 in the end of thesupport tube 43. Stationary support 46 includes a biasing mechanism 50disposed about the input shaft 42 at the opposite end of the operatorinput device 40.

[0016] The biasing mechanism 50 includes a first abutting member 52 thatis contacted by a post 54 when the operator input device 40 is rotatedin a first direction. When the operator input device 40 is rotated inthe first direction a second abutting member 56 makes contact with astationary post 58. Post 54 is connected to a transition plate 57 thatis operatively connected to the input shaft 42. While stationary post 58is connected to the support 46. The second abutting member 56 of thebiasing mechanism 50 also makes contact with post 54 when the operatordevice 40 is rotated in a second direction and the first abutting member52 contacts stationary post 58. The outer circumferential surface 59 ofthe transition plate 57 also includes a pair of stops (not shown) thatmake contact with the stationary post 58 so as to only allow theoperator input device 40 to rotate a predetermined amount. In thismanner the biasing mechanism 50 causes the operator input device 40 tobe self-centering when not being held and controlled by the operator.

[0017] Still referring to FIGS. 2 and 3, a braking device 60, which inthis example is an electromagnetic brake but may be any of a number ofbraking arrangements, is operatively connected to input shaft 42 and thesupport 46. A position sensor 62 monitors the rotational position of theinput shaft 42 relative to the support 44 and produces an electricalsignal indicative thereof. Position sensor 62 is a rotary position senorthat is connected to the end of the input shaft 42 and to the controlmodule 32 as by cable/wire. Position sensor 62 sends an output signal tothe control module 32 responsive to the magnitude and direction of therotation of input shaft 42. The braking device 60 is controlled andconnected to an activation switch 64. In this example, the termactivation switch 64 means any of a number of known switches that may beused to energize the braking device 60 from fully off position to aposition were the braking device 60 holds biasing mechanism 50 fromcausing the operator input device 40 to rotate bake to a centeredposition. Activation switch 64 may be positioned in an operator controlpanel (not shown) and when activated supplies a current to the brakingdevice 60 having a force sufficient enough to hold the input shaft 42 ina stationary manner without allowing the biasing mechanism 50 to centerthe operator input device 40. However, the operator can overcome thebraking force exerted by the braking device 60 during operation of thework machine 10 so as to make steering adjustments.

[0018] Industrial Applicability

[0019] In operation, the steering arrangement 14 used on a work machine10 such as an asphalt paver reduces operator fatigue and offersflexibility in several different ways. For example, if the work machineis operating in a straight-ahead operation or a slow curve, minimaloperator input to the steering system 14 through the use of the operatorinput device 40 is required. During these types of operations theoperator may choose to lock the steering arrangement 30 in apredetermined specific position. Closing the activation switch 64energizes the braking device 60. The force exerted by the braking device60 prevents the biasing mechanism 50 from returning the operator inputdevice 40 to a centered position, thus holding the operator input device40 in a stationary position relative to said support 46. As statedabove, the force exerted by the braking device 60 is greater than thebiasing mechanism 50, however, if steering adjustments are required theoperator can reposition the input device 40 even with the braking device60 energized. Thus, no change in signal from the position sensor 62 willbe sent to the control module 32 unless the operator desires a steeringcorrection.

[0020] The steering arrangement 14 also allows the operator to steer thework machine from either the left or right hand side of the work machine10. When the selector switch 38 is positioned to allow control signalsfrom the position sensor 62 of steering arrangement 30′, the operatorcan be seated on the right hand side of the work machine 10. This allowsthe work machine 10 to be maneuvered close to obstacles such as curbingon the right side of the machine 10. When the work machine 10 is shutdown at the end of operation and the ignition switch 36 is positioned inthe off position, the braking 60 is de-energized. This prevents anyinadvertent steering requests at the next work machine 10 start up.

1. A steering arrangement for a work machine having at least two groundengaging support members, each ground engaging support member having asteering motor connected thereto, each steering motor operativelypropelling and steering the respective ground engaging support member,said steering arrangement comprising: a support member; an operatorinput device movable relative to said support member; a biasingmechanism positioned between the support member and the steering inputdevice; a sensor operatively connected with said input device, andsensor producing an electrical signal indicative of the position of theinput device and said support; and an activation switch connected tosaid braking device.
 2. The steering arrangement of claims 1, whereinsaid braking device being an electromagnetic brake providing a brakingforce disallowing relative movement between said sterring input deviceand said support.
 3. The steering arrangement of claim 1, wherein saidbraking force is greater than the force exerted by said biasingmechanism.
 4. The steering arrangement of claim 1, wherein said brakingforce can be overcome to make steering adjustments.
 5. The steeringarrangement of claim 1, wherein said activation switch is actuatablebetween a fully of position and braking position.
 6. The steeringarrangement of claim 1, wherein said activation switch is manuallyoperated.
 7. The steering arrangement of claim 1, wherein said operatorinput device includes a steering wheel and a rotational input shaft. 8.The steering arrangement of claim 1, wherein said position sensor is arotary position sensor.
 9. A steering system for use in a work machinehaving at least two ground engaging support members, a pair of steeringmotors, one each being connected to each of the ground engaging supportmembers, and a propel pump connected to each of the steering motors inresponse to a steering signal, said apparatus comprising: a firststeering arrangement including; a support; a steering input devicemounted for relative movement to said support; and a braking deviceconnected to said steering input device and said support for providing abraking force so as to prevent relative movement between said steeringinput device and said support.
 10. The steering system of claim 9including; a second steering arrangement including; a support; asteering input device mounted for relative movement to said support; anda braking device connected to said steering input device and saidsupport for providing a braking force so as to prevent relative movementbetween said steering input device and said support.
 11. The steeringsystem of claim 10, including a selector switch connected to said firstand said second steering arrangement.
 12. The steering system if claim11, wherein said selector switch allows signals from said first steeringarrangement when said selector switch is in a first position and fromsaid second steering arrangement when said selector switch is in asecond position.
 13. The steering system of claim 9, including aposition sensor for monitoring the relative position of said input shaftand for producing an electrical signal indicative thereof.
 14. Thesteering system of claim 9, including an activation switch beingconnected to said braking device.
 15. The steering system of claim 14,wherein said activation switch is actuatable between a fully offposition and a braking position.
 16. The steering system of claim 15,wherein said braking force is greater than the force exerted by saidbiasing mechanism.
 17. The steering system of claim 15, wherein saidbraking force can be overcome to make steering adjustments.